GUATEMALA CITY, Guatemala (Reuters) - A strong earthquake hit southwestern Guatemala near the border with Mexico in the early hours of Wednesday, cutting power and injuring at least one person after a church collapsed, officials said.

The 6.9 magnitude quake damaged buildings in the neighboring southern Mexican state of Chiapas, authorities there said, but there were no immediate reports of deaths in either country.

"The earthquake was felt throughout the national territory and damage assessment has begun," said Julio Sanchez, spokesman for Guatemala's Conred national disaster center.

The earthquake hit 15 km (10 miles) west-northwest of the city of San Marcos, at around 1:30 am (3.30 a.m. ET) at a relatively deep 111 km, the United States Geological Survey reported.

An aftershock struck around 20 minutes later, the agency said.

Power went off in the Guatemalan departments of Retalhuleu, Quetzaltenango and Suchitepequez, authorities said. A church collapsed in San Sebastian, Retalhuleu, injuring one person, emergency services reported.